(rā'dē-ō-sŏnd') An instrument that is carried into the atmosphere by a balloon, makes measurements of temperature, air pressure, humidity, and wind speed and direction, and transmits the measurements back to the ground. A radiosonde is typically sent to altitudes of approximately 30 km (18.6 mi). There are approximately 70 radiosonde stations across the continental United States. Each station launches two radiosondes daily.

radiosonde

balloon-borne instrument for making atmospheric measurements, such as temperature, pressure, and humidity, and radioing the information back to a ground station. Special helium-filled meteorological balloons made of high-quality neoprene rubber are employed for elevating the radiosonde to very high altitudes of around 30,000 m (100,000 feet); maximum altitude for balloon-borne radiosondes is about 50,000 m